Properties of novel BZCY-(Li/Na)₂CO₃ composite electrolytes for LT-SOFC

BaZr_0.1Ce_0.7Y_0.2O_2.9 (BZCY) powder was synthesized by a homogeneous coprecipitation method, and the powder was mixed with carbonate to prepare the compound with different ratios of (Li/Na)₂CO₃. The structure and electrical properties of the composite electrolytes were characterized by SEM, XRD and TG-DTA. The results show that the carbonate in the amorphous form exists in the composite electrolytes, which reacts with BZCY to form BaCO₃. The conductivities of the composite electrolytes reach 0.095 S·cm^-1 at 600℃ and 0.071 S·cm^-1 at 450℃ in air, while 0.126 S·cm^-1 at 600℃ and 0.075 S·cm^-1 at 450℃ in humidified hydrogen. The conductivity of the composite electrolytes is basically stable for a long time in 0.08~0.09 S·cm^-1 within 400 h at 600℃. The single cell prepared with BZCY-20% (Li/Na)₂CO₃ composite electrolytes shows good output performance. The maximum power densities reach 741 mW·cm^-2 at 600℃ and 258 mW·cm^-2 at 500℃. When discharging with 0.6 A·cm^-2 at 600℃, the output performance is basically kept above 300 mW·cm^-2 within 90 min.